Silodosin has a selectively inhibitory effect against urethra smooth muscle constriction, and decreases urethra internal pressure without great influence on blood pressure. Furthermore, silodosin effects on an α1A-adrenoceptor subtype selectively, and is extremely useful as a therapeutic agent for dysuria associated with benign prostatic hyperplasia and the like (see Patent References 1 and 2).
As an effective and efficient method for production of silodosin, it is proposed or reported that an optically active amine compound represented by the following general formula:
wherein R1 represents a hydrogen atom or a hydroxyl-protective group, is allowed to react with a phenoxyethane compound represented by the following general formula:
wherein X represents a leaving group, and optionally deprotected and the cyano group is converted to a carbamoyl group (see Patent References 3 and 4).
However, in the above-mentioned methods for production, a dialkyl compound (C) represented by the following general formula:
wherein R1 represents a hydrogen atom or a hydroxyl-protective group, is sometime generated as a by-product because of the reaction of one molecule of the optically active amine compound and two molecules of the phenoxyethane compound. Since it is difficult to remove the by-product by purification method used in a common industrial production such as recrystallization or the like, it is necessary to use purification method such as column chromatography or the like to remove the by-product. Therefore purification processes tend to be complex, are not satisfactory a method for industrial production. Thus, the development of a more applicable purification method for industrial production is required.    Patent Reference 1: Japanese Patent Publication H6-220015;    Patent Reference 2: Japanese Patent Publication 2000-247998;    Patent Reference 3: Japanese Patent Publication 2001-199956;    Patent Reference 4: Japanese Patent Publication 2002-265444.